1. Field of the Invention
The present invention relates to an air conditioning system capable of preventing a harmful gas or harmful fine particles from intruding into the air conditioning space as much as possible.
2. Description of the Related Art
Conventionally, an automobile is equipped with an air conditioner having an outer air introduction mode of introducing air from outside the cabin and feeding it into the cabin after heating or cooling the air and an inner air circulation mode of heating or cooling air in the cabin while circulating the air. In recent years, for example, the precision of vehicle assembly has increased as a measure for enhancing the performance of blocking intrusion of noise into the cabin, and the closing off of cabin has also increased.
When the closing off of a vehicle cabin is increased in this way, when several occupants ride in the vehicle for a long time, reduction of oxygen concentration or an increase in carbon dioxide concentration occurs and the occupants may suffer from headaches or feel uncomfortable. In order to solve this problem, there is known a technique of using a filter having a permeation membrane capable of discharging carbon dioxide out of the cabin and allowing the permeation of oxygen from the outside of the vehicle cabin into the cabin, thereby preventing an increase in carbon dioxide concentration and decrease of oxygen concentration in the vehicle cabin while maintaining a comfortable interior (see, for example, Japanese Unexamined Patent Publication (Kokai) No. 2004-203367).